Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a)(147-25)-(-25+147-49)
=122-73
=49
b)57.(-28)+72.(-57)
=57.(-28-72)
=57.(-100)
=-5700
a.(147-25)-(-25+147-4)
= 147 - 25 + 25 - 147 + 4
= (147 - 147) + ( 25 - 25) + 4
= 0 + 0 + 4
= 4
b.57.(-28)+72.(-57)
= 57 . (-28) + (-72) . 57
= 57.((-28) + (-72))
= 57 . -100
= - 5700
Trần Tuyết Tâm
1+5+9+13+17+...+x=501501
(x+1)[(x-1):4+1]:2=501501
(x+1)[(x-1).1/4+1].1/2=501501
(x+1)(1/4x-1/4+1).1/2=501501
[(x+1).1/4x-(x+1).1/4+(x+1)].1/2=501501
[(x+1)(-1/4+1)+(x+1).1/4x].1/2=501501
[(x+1).3/4+(x+1).1/4x].1/2=501501
(x+1)(3/4+x/4).1/2=501501
(x+1)[(3+x)/4] .1/2=501501
(x+1)[(3+x)/8] =501501
[(x+1)(3+x)]/8=501501
(x+1)(3+x)=4012008
3x+x^2+3+x=4012008
x^2+4x+3=4012008
x^2+x+3x+3=4012008
x(x+1)+3(x+1)=4012008
(x+1)(x+3)=4012008
(x+1)(x+3)=2002.2004
suy ra x+1=2002 và x+3=2004
x=2001 ; x=2001
vậy x=2001
Ta có : 5 =2+3 ; 9=4+5; 13=6+7;17=8+9
Do đó ta có x = a+(a+1) (với a thuộc N)
Nên 1+5+9+13+17+...+x =1+2+3+4+5+6+7+...+a+(a+1)=501501
Hay (a+1)(a+2)=1003002=1001.1002
Suy ra a=1000
x= 1000+(1000 +1)
x+2001
vậy x bằng 2001
Câu 1:a) \(\left(\frac{-5}{12}+\frac{6}{11}\right)+\left(\frac{7}{17}+\frac{5}{11}+\frac{5}{12}\right)\)
\(=\left(\frac{-5}{12}+\frac{5}{12}\right)+\left(\frac{6}{11}+\frac{5}{11}\right)+\frac{7}{17}\)
\(=0+1+\frac{7}{17}\)
\(=\frac{17}{17}+\frac{7}{17}\)
\(=\frac{24}{17}\)
b) \(\frac{7}{12}-\left(\frac{5}{12}-\frac{5}{6}\right)\)
\(=\frac{7}{12}-\frac{5}{12}+\frac{5}{6}\)
\(=\frac{7}{12}-\frac{5}{12}+\frac{10}{12}\)
\(=\frac{7-5+10}{12}\)
\(=1\)
c) \(\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}\)
\(=\frac{1}{12}+\frac{1}{30}\)
\(=\frac{5}{60}+\frac{2}{60}\)
\(=\frac{7}{60}\)
Câu 2:a) \(\frac{x}{8}=2+\frac{-3}{2}\)
\(\Leftrightarrow\frac{x}{8}=\frac{4-3}{2}\)
\(\Leftrightarrow\frac{x}{8}=\frac{1}{2}\)
\(\Leftrightarrow2x=8\)
\(\Leftrightarrow x=\frac{8}{2}\)
\(\Leftrightarrow x=4\)
b) \(\frac{-5}{6}+\frac{8}{3}+\frac{29}{-6}\le x\le\frac{-1}{2}+2+\frac{5}{2}\)
\(\Leftrightarrow\frac{-18}{6}\le x\le4\)
\(\Leftrightarrow-3\le x\le4\)
\(\Leftrightarrow x\in\left\{-3;-2;-1;0;1;2;3;4\right\}\)
B= 1+2+22+23+.....+22015
2B = 2+22+23+24+.....+22016
2B - B = 22016 - 1
=> B = 22016 - 1
